Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUS2734033 A
Publication typeGrant
Publication dateFeb 7, 1956
Filing dateOct 8, 1949
Publication numberUS 2734033 A, US 2734033A, US-A-2734033, US2734033 A, US2734033A
InventorsJames Z. Menard
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
US 2734033 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent() MAGNETIC RECORDlNG MEDIUM James Z. Menard, Summit, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a

This invention relates to magnetic recording media.

For those applications Where the message must be changed frequently, magnetic recorders are a logical solution. There are a number of commercial applications for magnetic recording which require continuous repetition of messages between and 30 seconds in length. Some of these applications are for weather announcements, various intercept services, toll circuit delay quotations, and service quotations such as in the airline oices and in stock exchanges.

For such uses it is desirable that the recorder have acceptable transmission characteristics and particularly that it require little maintenance and give long life. It is possible to realize acceptable transmission performance from several existing types of magnetic media but it is much more difcult to achieve the life and reliability desired for these types of service. Magnetic recording systems with practically indefinite life can be built by operating with the heads physically separated from the medium by a small air-gap. However, separation betweenheads and medium causes loss of signal and band width, and for the separations which can be used in a realizable system, it is necessary to increase the speed of the medium by an appreciable factor to compensate for these losses. This increases the required amount of recording medium to such an extent that it is not practicable to construct out-of-contact recorders for the message length desired in these services. Therefore, it is virtually necessary to operate with the heads in contact with the recording media.

A loop of vicalloy steel tape has been used for several years in systems such as those employed for weather announcements. While these systems have given satisfactory results, the procurement of vicalloy tape does present some diculties. Experience with loop-type magnetic recorder-reproducers has indicated that most fail ures are due to physical failure of the tape as a result of the continuous tension, flexion, and abrasion it undergoes. In machines using paper or plastic tapes, the tapes have failed physically before the coatings showed serious deterioration, but it is probable that the life of the coating, which is about 0.0005 inch thick in commercial tapes, would become a limitation if appreciable improvement were realized in the physical life of the paper or plastic backing.

This experience has suggested the desirability of placing the medium on the surface of a cylinder which is rotated under the recording heads, using a spiraling arrangement or a head switching arrangement to increase the track length in those applications where the cylinder circumference is insuflicient to give the necessary recording time. With such an arrangement the medium would not be manipulated and, in those applications where it is necessary to operate with the recording head in contact with the recording medium, it would be stressed only in compression by the weight of the recording head. Physical failure would be virtually eliminated and the life of the "ice medium should be limited primarily by the wear occurring between the medium and thel recording head.

Two classes of material have appeared promising as magnetic media for use on cylinders. These are magnetic platings and powdered magnetic coatings. Magnetic sufaces have been produced on cylinders by a superposed alternating current-direct current electroplating process. Such a coating does not easily deteriorate, and gives a high signal output. However, it is vitally important to maintain consistent intimate contact between the recording heads and recording medium because any separation decreases the signal output and deteriorates the frequency response. As an example, separation of one Wavelength between head and medium causes approximately 55 decibels loss in output at that frequency. With the plated media it is diicult to maintain the desired intimacy of contact because neither the heads nor the media can yield appreciably to conform to slight irregularities in the contacting surfaces of the head and medium, or to accommodate inaccuracies in the mechanical system.

Experience has shown that a metallic head riding on a plated surface may under some conditions decrease the life of the recording medium to an undesirable degree. Moreover, the frequency response and signal-tonoise ratio of the plated media are usually poorer than the frequency response and signal-to-noise ratio of the powdered media.

The powdered magnetic recording media are relatively new, but have achieved wide usage in the form of coated tapes. They ofrer certain advantages over the plated rnedia with regard to improved frequency response, better sgnal-to-noise ratio, and economy and ease of produc tion. Some work has been reported on the use of powdered magnetic coatings on cylinders for pulse storage calculators, but these have been used at high speed with the recording heads out of contact, and they accommodate only a short recording time. To obtain recording times of the length required for the applications in which the present invention is to be employed, it is necessary to operate with the recording head in contact with the recording medium. Therefore, it is desirable to provide a powdered recording medium in such form that it will wear Well, and possess enough resiliency to accommodate contact irregularities thereby maintaining intimate con tact between the heads and the medium, and to cushion the heads against chatter.

Accordingly, it is an object of the present invention to provide a new and improved magnetic recording medium which will possess the properties enumerated above.

lt has been discovered that a recording medium comprising a cured rubber and finely divided or powdered ferromagnetic material will satisfactorily meet the requirements for contact wear, resiliency, cushioning of the contacting recording head against chatter, permanency of recording, frequency response, signal-,to-noise ratio, and economy and ease of production. This medium may be molded in tire form and then slipped onto and atixed to the surface of a recording cylinder, or, it may be applied directly to the recording cylinder by spraying or dipping. The recording medium is cured or vulcanized in any manner known to the art before it is employed in the recorder-producer system.

The invention itself, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

Fig. l is a perspective of the recording cylinder with the recording medium aixed to the surface thereof;

Fig. 2 is a cross-section of the cylinder and medium shown in Fig. l; and

Fig. 3 is a perspective of the recording medium.

As shown in Figs. l and 2, the recording medium 4 dipping and spraying.

is aixed tothe recording cylinder 2 in such manner as to provide a surface upon which a magnetic recording head may ride smoothly and with continuous intimate contact during the recording or reproducing process. The

`recording cylinder 2 may be of any nonmagnetic material such as aluminum. .T he recordingmedium 4- comprises a rubber and a finely divided ferromagnetic material whichhave been intimately mixed as by milling. Any synthetic or natural rubber and any magnetic oxide having a grain'size less than one micron will, when combined to form the medium, provide satisfactory magnetic recording properties. Iron oxide concentrations in the range of 40 per cent to 75 per cent by weight have been employed and have been found to provide satisfactory transmission properties. Satisfactory resiliency and recording head cushioning has been obtained with media having a thickness of not less than 1&4 inch.

Satisfactory media have been produced by moulding, Moulding appears to offer the most economical and most easily controlled production process, while spraying of the medium directly onto the recording cylinder appears to produce slightly better transmission qualities. Spraying or dipping provides a coating on the cylinder which might be dened as permanent, While moulding provides a medium in the form of a replaceable belt or tire for the recording cylinder.

The medium in the form of a replaceable belt or tire is shown in Fig. 3.

It has been found that some advantages may be gained with regard to the quality of the medium surface upon which the recording head rides if a lubricant such as graphite, or wax, in concentrations up to 5 per cent by weight, is added to the composition of rubber and magnetic oxide prior to or during the milling operation.

A satisfactory composition, which may be taken as a specic example of the manner in which the invention may be practiced, was prepared by milling 100 parts of neoprene with 100 parts of magnetic iron oxide, 3 parts of paraffin Wax, 4 parts of magnesium oxide and 5 parts of zinc oxide. This compound was then moulded and cured, and aixed to the recording cylinder inthe form of an endless belt or tire.

It is to be understood that the above-described arrangements are illustrative of the application of the principles of the invention. Other arrangements may be devised by those skilled in the art Without departing from the spirit and scope of the invention.

What is claimed is:

A sound record medium molded and cured into a ilexible, collapsible, radially extensible endless band of substantially uniform thickness, consisting of .parts of neoprene intimately mixed With 100'parts of finely divided magnetic iron oxide, 3 parts of paraflin wax, 4 parts of magnesium oxide and 5 parts of Zinc oxide, vsaid record medium being mountable under radial tension and operable in intimate, continuous, yielding contact With an electromagnetic transducer.

References Cited in the file of this patent UNITED STATES PATENTS 96,237 Johnson Oct. 26, 1869 900,392 Kirkegaard Oct. 6, 1908 1,653,467 ONeill Dec. 20, 1927 1,671,228 Cherry May 29, 1928 1,671,426 Holland May 29, 1928 1,731,483 Fisher et al. Oct. 15, 1929 1,847,860 Best Mar. 1, 1932 1,879,722 Walton Sept. 27, 1932 1,887,021 Henderson Nov. 8, 1932 1,994,534 Robinson Mar. 19, 1935 2,229,293 Huntley et al. Ian. 21, 1941 2,446,387 Peterson Aug. 3, 1948 2,496,047 Goddard Jan. 31, 1950 FOREIGN PATENTS 340,705 Great Britain Jan. 8, 1931 418,096 Great Britain Oct. 18, 1934 459,884 Great Britain Jan. 18, 1937

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US96237 *Oct 26, 1869 Improved rubber compound for packing
US900392 *Mar 5, 1908Oct 6, 1908Stilson HutchinsSound recording and reproducing instrument.
US1653467 *Mar 22, 1926Dec 20, 1927Joseph A. O'neillRecord for reproducing sound tones and action
US1671228 *Sep 13, 1923May 29, 1928Cutler Hammer Mfg CoSound record
US1671426 *Jul 21, 1926May 29, 1928Holland Charlotte MaryPhonograph needle
US1731483 *Apr 14, 1924Oct 15, 1929Goodrich Co B FRubber composition and method of making and shaping the same
US1847860 *Jan 23, 1929Mar 1, 1932Frank M BestSound record and method of making the same
US1879722 *Nov 10, 1930Sep 27, 1932Walton Alfred LeonardNeedle for sound reproducing instruments
US1887021 *Oct 4, 1930Nov 8, 1932Henderson William ArmstrongImprovement in reproducing sound from records tracked by alpha stylus
US1994534 *Apr 19, 1933Mar 19, 1935Rca CorpInductance coil and method of manufacture thereof
US2229293 *Jun 14, 1938Jan 21, 1941C W B Dev CoMagnetic recording system
US2446387 *May 19, 1943Aug 3, 1948Peterson Thomas FShielded cable
US2496047 *Jun 18, 1947Jan 31, 1950Rca CorpArt of recording and reproducing two-sided magnetic records
GB340705A * Title not available
GB418096A * Title not available
GB459884A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2862845 *Oct 25, 1954Dec 2, 1958Clevite CorpMagnetizable bands
US2880279 *Jun 12, 1953Mar 31, 1959Bell Telephone Labor IncSound recording and reproducing apparatus
US2907680 *Jan 23, 1958Oct 6, 1959IbmStress relieved thin magnetic films
US3007807 *Mar 25, 1958Nov 7, 1961Audio Devices IncMagnetic recording
US3026587 *Jun 28, 1955Mar 27, 1962Spencer William RobertMagnetic rubber tobacco priming bands
US3040386 *Aug 29, 1957Jun 26, 1962Bell Telephone Labor IncMethod of fabricating a laminated magnetic recording sleeve
US3081264 *Mar 30, 1959Mar 12, 1963Matake KurokawaMethod of preparing a magnetic recorder powder
US3387993 *Oct 16, 1964Jun 11, 1968AmpexMagnetic tape with a lubricant containing mineral oil and fatty acid amide in the magnetic coating
US3423233 *Jan 25, 1965Jan 21, 1969Fuji Photo Film Co LtdMagnetic recording element
US3510489 *Jul 31, 1968May 5, 1970IbmWeb fabrication process
US3542589 *Mar 27, 1968Nov 24, 1970Basf AgMagnetic recording media having high abrasion resistance
US4123784 *Jan 31, 1977Oct 31, 1978Isamu IchiugiSelectable fraction of revolution tape recorder
US4132827 *Jan 18, 1977Jan 2, 1979Fuji Photo Film Co., Ltd.Carbon black
US5234762 *Nov 14, 1991Aug 10, 1993Eastman Kodak CompanyCompliant support with mutually adhered web for transfer of information
US5448419 *Jun 11, 1993Sep 5, 1995Eastman Kodak CompanyApparatus and method for anhysteretically recording from master drum to slave web
DE1221282B *Sep 17, 1963Jul 21, 1966Sony CorpSchicht fuer ein Fernsehsignalaufzeichnungsband
U.S. Classification252/62.54, 360/131, 524/552, 360/136, 523/174, 260/998.16
International ClassificationC09D5/23, G11B5/004
Cooperative ClassificationG11B5/004
European ClassificationG11B5/004